Simulation of volcanic effects on
global solar insulation model
Mari Masdal, Jonas Coyet, Morven Muilwijk & Nikolai Aksnes
2013
SIO 217a Atmospheric and Climate Sciences I
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Introduction
Model & theory
Effects of volcanic eruptions on insolation
Implementing the effect of volcanoes in our
model
• Results
• Conclusion
Introduction
• Reproduce fig. 12.3 in
“Thermodynamics of Atmospheres &
Oceans”
• Show the effect of the recent
volcanic eruption in Iceland in this
model and compare to the Pinatubo
and El Chichon eruptions
• Mean insolation at a given
time and latitude
• Lines of constant solar heat
flux
• Polar nights
• Seasons due to declination
angle and elliptical earth
orbit
Theory and model
• The mean daily insolation (curve values in the plot) is given by:
• Where S is the solar flux and is calculated from
•f
is the square of the mean sun-earth distance
• Z is the solar zenith angle
Solar zenith angle
• The solar zenith angle depends on the latitude,
season and time of day
• Hour angle ψ
• Declination angle δ
• Latitude Φ
Model reproduction
Seasons due to declination angle
Volcano eruptions and climate
Ways volcanos affects climate:
1.
2.
3.
Increased greenhouse effect
Local covering due to ash clouds
Cooling effect due to sulfur aerosols
“Eruption size V.S. amount of sulfur emitted“
Cooling due to sulfur aerosols
«Haze effect»
• Sulfur + water vapor  sulfuric acid
 Dense clouds of H2SO4 dropplets
 Efficient scattering
 Increased albedo
Pinatubo eruption and Eyafjallajokull eruption
• Pinatubo, 1991
Philiphines
20,000,000 tonnes sulfur emmited
Global mean temperature dropp
of 0.5 C over 1-3 years
Eyafjallajokull, 2010
Iceland
Approx. 10-15,000 tonnes sulfur
emitted.
Climate effect?
El Chicon, 1982
Mexico
~7,000,000 tonnes sulfur emmited
smaller climate effect
Spreading of the Pinatubo aerosol cloud
Spreading of the Pinatubo aerosol cloud
Iceland ash cloud spreading
Huge cloud, but why no climate effect?
Simulating the effect of Pinatubo in our model
• Why we choose Pinatubo for our simulation?
• Possible change: difference in albedo
• Global measurements:
- Decrease in global mean tempearature 0.5 C
• Ship measurements:
- solar flux insolation decreased with 1.4%-4.1%
- optical thickness increased from 0.1 to 0.3
• Assumption: all change in insolation is due to sulfur aerosols (netto effect)
Approach 1 : equatorial
Decrease in solar insolation
of 1.4%-4.1%
Using Simplified Climate Model
Approach 2:
Decrease in global albedo of 1.5% based on average temp increase at
surface
Summary and conclusion
We have successfully reproduced the model
 Even though our two approaches differ some
in result we approximate them to give the same
average result